In the case of a land vehicle, the auxiliary aiming function consists in orientating a weapon carried by the vehicle whereas, in the case of a torpedo, the auxiliary aiming function consists in piloting the torpedo.
For such vehicles (armored vehicles or torpedos), inertial navigation, such as applied to airborne vehicles, proves to be expensive to manufacture and, in addition, does not seem to be adapted to the needs, in particular for the aiming function: in fact, the principle of such inertial navigation is based on the use of gyroscopes and accelerometers and the results supplied are the outcome of the pure and simple integration of the accelerations without any provision of an indication concerning the measured speed with respect to the surrounding environment: the possible performances, such as those obtained with installations of aeronautical origin whose characteristic is of the order of one nautic mile/hour) are ridiculous for a land vehicle.
Installations have therefore been proposed, for land and sea vehicles, using the speeds measured with respect to the sourrounding environment, these installations being based on an integration of these measured scalar speeds by using a directional heading reference and, possibly, a vertical reference.
Thus, very simple installations have been proposed comprising free gyros used as vertical references and free gyros used as North indicators; however, the measurements obtained are relatively inaccurate, because of the inaccurate directional characteristics.
More complex installations have also been proposed comprising, on the one hand, a thread suspension gyro used as North detector when the land vehicle is stopped and, on the other hand, a so-called "directional" gyro with two degrees of freedom stabilizing a dual gimbal system and used while the vehicle is travelling: from the indications supplied by these two elements, and by measuring the speed with respect to the surroundings, it is then possible to obtain a relatively accurate measurement of the movements, to detect and keep the heading with errors of the order of 1 mrd and 1 mrd/hour respectively.
In any case, the installations which have just been discussed above do not allow the parameters characterizing the trajectory of the vehicle to be known, and possibly controlled, and the gyrometric systems for providing the auxiliary aiming or piloting function are separate (case of different positions in the vehicle or case of different pass bands).
These systems are moreover set up in different positions in the vehicle, depending on the nature of the vehicle and the nature of the auxiliary aiming function (e.g. stabilization of a gun).
The aim of the invention is precisely a gyroscopic navigational installation grouping together, in one and the same apparatus, the elements for controlling the parameters characterizing the linear trajectory of the vehicle with good performances (e.g. measurement of the azimuth with a drift equal to or less than 1 degree/hour, detection of the vertical to a tenth of a degree) and for providing the auxiliary aiming function as previously defined with a high pass-band as is required by this kind of function and a high angular sensitivity (e.g. a pass-band of the sensing members of 30 to 50 Hz and a short term angular sensitivity equal to or less than 0.3 mrd), which corresponds to the characteristics required for stabilizing a gun.
It is known that solutions of this type have already been described or developed: it is a question of systems having two or three gyros (two or three depending on whether the technology of single or double axis gyros is used) which have axes of sensitivity on a trirectangle trihedron, and are connected to the vehicle.
With this arrangement, the gyro wheels must accompany all the angular movements of the vehicle through very stiff electronic gyrometric loops (pass-band of about 50 Hz).
These systems are opposed to the older systems which, on the contrary, used three successive stabilized gimbals (roll, pitch and azimuth for example), the central-most gimbal carrying the gyros which were then used as a zero apparatus in so far as the measurement of the angular speeds is concerned.
More recently, the cases of the gyros are connected to the structure of the vehicle; efforts are made to achieve the navigational function while using the available gyrometric measurements for an aiming function with a high passband; however, the major defect of these solutions is very complex coupling when, from analog measurements, delivered by the gyros, it is desired to re-calculate the attitude of the vehicle (heading, roll, pitch).
It is then necessary to use very complicated calculations which are only possible with a miniaturized on-board computer (calculations of 300,000 operations per second), which calculations need to be effected with a double length (typically 32 bits). It is then necessary to compensate in real time, within 10.sup.-4, the conical motion deflections which appear when each input axis of each gyro describes a cone, which deflections are of the orders of magnitude of a few thousandths of a degree/hour, even if the alternate angular movements of the vehicle are of the order of a few degrees.